Single crystal zirconium niobium tungsten alloy and preparation method thereof

Abstract

The invention belongs to the technical field of metal material preparation, and particularly relates to a single crystal zirconium niobium tungsten alloy and a preparation method thereof. The Zr-Nb-W alloy comprises the following elements in percentage by weight: 20.0 to 28.0 percent of Nb, 8.0 to 12.0 percent of W, and the balance of Zr and inevitable impurities. The method comprises the following steps: pretreating zirconium, niobium and tungsten metal raw materials, sub-packaging the pretreated raw materials into a first sample, carrying out vacuum arc melting, preparing a button ingot, crushing the button ingot, reassembling and sub-packaging to obtain a second sample; remelting the second sample by adopting laser to obtain a spherical zirconium-niobium-tungsten alloy sample; an electrostatic suspension system is adopted to circularly heat and cool a spherical zirconium-niobium-tungsten alloy sample, so that a liquid alloy reaches a deep supercooled state and is rapidly solidified to form the spherical single crystal zirconium-niobium-tungsten alloy, the high-temperature mechanical property and creep resistance of the zirconium-niobium-tungsten alloy are improved, and the material can still keep excellent service performance in an extreme environment.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of metal material preparation, and particularly relates to a single-crystal zirconium niobium tungsten alloy and a preparation method thereof. BACKGROUND

[0002] As a high-performance alloy, the addition of zirconium improves the oxidation resistance of the alloy, niobium provides solid solution strengthening effect, and tungsten significantly improves the high-temperature strength and creep resistance. In the nuclear industry, zirconium niobium tungsten alloy has become an ideal material for nuclear reactor fuel cladding and coolant pipes due to its low neutron capture cross section and resistance to irradiation swelling, and has shown key application value in fusion reactor projects. The body-centered cubic structure of zirconium niobium tungsten alloy can form long and continuous jets under explosive loading conditions. The current zirconium niobium tungsten alloy liner has been applied to precision guided munitions such as terminal-sensitive bombs. The addition of tungsten element can improve the material density, which is beneficial to further improve the penetration and damage capability of key components of zirconium niobium tungsten alloy warheads.

[0003] Currently, zirconium niobium tungsten alloy is mostly polycrystalline structure. This polycrystalline structure is prone to grain boundary sliding and diffusion creep at high temperatures, which deteriorates the structural performance of the material. Single crystal structure can eliminate grain boundaries, thereby greatly improving high-temperature mechanical properties and creep resistance, so that the material can still maintain excellent performance in extreme environments, and can significantly improve the thrust-to-weight ratio and aircraft performance. However, the preparation of single-crystal zirconium niobium tungsten alloy currently has the following problems:

[0004] The preparation of general single-crystal alloys is mainly realized by directional solidification technology, the core of which is to control the preferential growth of crystals along a specific direction to obtain a single crystal structure. Typical methods include the Bridgman method and the zone melting method. By precisely controlling the temperature gradient and solidification rate, the melt forms a single crystal under the action of directional heat flow. However, the pulling speed needs to be accurately controlled during the preparation process, and the industrial window is narrow. Modern technology also combines seed crystal induction technology to pre-place a single crystal seed to determine the crystal orientation, supplemented by electromagnetic fields or vibrations to suppress the formation of impurities. For high-temperature alloys, high-speed solidification or liquid metal cooling methods are often used. The process difficulty lies in the suppression of impurities and defect control, which requires optimization of parameters through computer simulation.

[0005] Therefore, how to prepare high-quality single-crystal zirconium niobium tungsten alloy by a simple method is a difficult problem to be overcome. SUMMARY

[0006] In order to solve the above technical problems, the present application provides a single-crystal zirconium niobium tungsten alloy and a preparation method thereof. The liquid zirconium niobium tungsten alloy is brought to a deep undercooling state by using electrostatic suspension technology, and a single crystal structure is formed during rapid solidification. On the one hand, the deep undercooling condition can significantly suppress element segregation and improve the uniformity of chemical composition. On the other hand, rapid solidification can effectively shorten the solidification time and improve the preparation efficiency.

[0007] The electrostatic suspension technology is an advanced technology for realizing containerless suspension of materials by balancing gravity with electrostatic field force, and the core principle thereof is to form a strong electric field by applying a potential difference between two parallel metal plates, so that the charged metal is stably suspended under the balance between the electric field force and the gravity. In addition, the system works in a high vacuum environment, which can effectively isolate oxygen and avoid high-temperature oxidation of high-activity metals, and the feature of no container contact eliminates heterogeneous nucleation points, so that the materials can realize ultra-high temperature melting and deep undercooling rapid solidification, and an ideal superstate working platform is provided, which provides a new idea for the preparation of zirconium-niobium-tungsten alloy single crystals.

[0008] The present application is realized by the following technical solutions.

[0009] The present application provides a preparation method of single crystal zirconium-niobium-tungsten alloy, comprising the following steps: Step one: the surfaces of high-purity zirconium, niobium and tungsten metals are polished and cleaned by sandpaper and anhydrous ethanol, and the pretreated raw materials are divided into first samples, and the first samples are subjected to multiple vacuum arc melting to prepare button ingots, the button ingots are crushed and then reassembled and divided into second samples. The mass percentage composition of the zirconium-niobium-tungsten alloy is as follows: Nb: 20.0wt.%-28.0wt.%, W: 8.0wt.%-12.0wt.%, and the balance is Zr and unavoidable impurities, and the total amount of each element is 100%. It should be noted that Zr has good activity, and the addition of Nb can improve the plasticity of the material, and the addition of W can increase the density of the material and also realize precipitation strengthening. It should be noted that the addition of W element should not be excessive. Excessive W element is easy to form a polycrystalline structure.

[0010] Step two: the second sample is remelted by laser to obtain a spherical zirconium-niobium-tungsten alloy sample.

[0011] Step three: the spherical zirconium-niobium-tungsten alloy sample is subjected to multiple cyclic heating and cooling by an electrostatic suspension system to obtain a deep undercooling degree, and a spherical single crystal zirconium-niobium-tungsten alloy is rapidly solidified.

[0012] Preferably, the surfaces of the metal raw materials are polished and cleaned by sandpaper and anhydrous ethanol before use. The purity of the zirconium, niobium and tungsten metals is not less than 99.9%.

[0013] Preferably, during the pretreatment, the weighing precision of the metal raw materials during the division of the first samples is 0.1mg, the element ratio is calculated, and during the calculation, the total amount is 800-1000mg per sample.

[0014] Preferably, during the vacuum arc melting, an extra piece of high-purity zirconium metal is put into the same furnace and is first melted.

[0015] Preferably, the first sample undergoes 2 to 4 vacuum arc melting cycles, with a melting current of 200A to 250A and a pre-melting vacuum degree of 10. -4 ~10 -3 Pa.

[0016] Preferably, the mass of the second sample is 70~90mg / sample.

[0017] Preferably, when laser remelting the second sample, the number of laser melting operations is 1 to 3, and the laser melting emitter power is 20 to 30W.

[0018] Preferably, during the electrostatic levitation process, laser heating is used, with the laser emitter power parameter being 35~50W, the heating and cooling cycle number being 3~6 times, resulting in a supercooling degree of 350K~385K.

[0019] The present invention also provides a single-crystal zirconium-niobium-tungsten alloy prepared by the above preparation method.

[0020] Compared with the prior art, the present invention has the following beneficial effects: This invention selects specific amounts of components and combines vacuum arc melting and laser remelting processes to improve the uniformity of the composition. Then, using electrostatic levitation technology, a single-crystal zirconium-niobium-tungsten alloy was successfully prepared. Specifically, the alloy composition of this invention is Nb 20.0wt.%~28.0wt.%, W 8.0wt.%~12.0wt.%, with the balance being Zr and unavoidable impurities, totaling 100%. Zr has good activity, while the addition of Nb can improve the material's plasticity. The addition of W can increase the material's density and also achieve precipitation strengthening. It is important to note that the addition of W should not be excessive, as excessive W can easily lead to the formation of a polycrystalline structure. The zirconium, niobium, and tungsten metal raw materials are pretreated, and the pretreated raw materials are packaged into first samples and subjected to multiple vacuum arc melting processes to prepare button ingots. During the vacuum arc melting stage, the ingots are repeatedly flipped up and down to prevent the denser tungsten from settling to the bottom during melting, thus avoiding uneven alloy composition. Furthermore, during the vacuum arc melting stage, high-purity zirconium metal is pre-melted to absorb residual oxygen and impurities in the furnace chamber, thereby improving the melting purity of the target zirconium-niobium-tungsten alloy. The button ingots are then broken, reassembled, and packaged to obtain a second sample. This second sample is then repeatedly remelted using a laser to obtain spherical zirconium-niobium-tungsten alloy samples. An electrostatic levitation system is then used to repeatedly cycle the heating and cooling of these spherical samples to achieve deep undercooling, resulting in rapid solidification and the formation of spherical single-crystal zirconium-niobium-tungsten alloy. This invention utilizes electrostatic levitation technology to replace traditional directional solidification and seed crystal induction techniques, significantly improving the efficiency of single-crystal preparation. The deep undercooling rapid solidification technology induces a solute trapping effect, thereby improving the uniformity of the chemical composition. The electrostatic levitation process achieves deep undercooling and rapid solidification to form a single-crystal structure, improving the high-temperature mechanical properties of the alloy.

[0021] This invention achieves a single-crystal microstructure in zirconium-niobium-tungsten alloy through the synergistic effect of alloy composition and process. Furthermore, the preparation method of this invention is simple and the preparation process is easy to control, providing methodological support for the preparation of single-crystal zirconium-niobium-tungsten alloys, which is beneficial for further improving the performance of zirconium-niobium-tungsten alloys and expanding their application range. Attached Figure Description

[0022] Figure 1 The image shows the EBSD diagram of the zirconium-niobium-tungsten alloy prepared in Example 1.

[0023] Figure 2 The image shows the EBSD diagram of the zirconium-niobium-tungsten alloy prepared in Example 2.

[0024] Figure 3 The image shows the EBSD diagram of the zirconium-niobium-tungsten alloy prepared in Example 3.

[0025] Figure 4 The image shows the EBSD diagram of the zirconium-niobium-tungsten alloy prepared in Comparative Example 1.

[0026] Figure 5 EBSD image of the zirconium-niobium-tungsten alloy prepared for Comparative Example 2. Detailed Implementation

[0027] To enable those skilled in the art to better understand and implement the technical solutions of the present invention, the present invention will be further described below with reference to specific embodiments and accompanying drawings. However, the embodiments described are not intended to limit the present invention. Unless otherwise specified, the experimental methods and detection methods described in the following embodiments are conventional methods; unless otherwise specified, the reagents and materials described are commercially available.

[0028] This invention provides a method for preparing a single-crystal zirconium-niobium-tungsten alloy, the method comprising the following steps: Step 1: Use sandpaper and anhydrous ethanol to polish and clean the surface of high-purity zirconium, niobium and tungsten metals. Pack the pretreated raw materials into the first sample, perform vacuum arc melting to prepare button ingots, break the button ingots and reassemble and package them to obtain the second sample. Step 2: The second sample is remelted using a laser to obtain a spherical zirconium-niobium-tungsten alloy sample; Step 3: The spherical zirconium-niobium-tungsten alloy sample is subjected to cyclic heating and cooling using an electrostatic levitation system to obtain deep undercooling and rapid solidification to form a spherical single-crystal zirconium-niobium-tungsten alloy.

[0029] In a preferred embodiment of the present invention, in step one, the zirconium-niobium-tungsten alloy has the following mass percentage composition: Nb: 20.0 wt.%~28.0 wt.%, W: 8.0 wt.%~12.0 wt.%, with the balance being Zr and unavoidable impurities, and the total amount of all elements is 100%.

[0030] In a preferred embodiment of the present invention, in step one, when the first sample is packaged, the weighing accuracy of the metal raw material is 0.1 mg, the ratio of each element is calculated, and the total reference amount is 800~1000 mg / sample.

[0031] In a preferred embodiment of the present invention, in step one, during vacuum arc melting, an additional piece of high-purity zirconium metal is placed in the same furnace for subsequent vacuum arc melting and is melted first.

[0032] In a preferred embodiment of the present invention, in step one, the vacuum arc melting process is carried out 2 to 4 times.

[0033] In a preferred embodiment of the present invention, in step one, during vacuum arc melting, the melting current is 200A~250A, and the pre-melting vacuum degree is 10. -4 ~10 -3 Pa.

[0034] In a preferred embodiment of the present invention, the mass of the second sample is 70mg / sample to 90mg / sample.

[0035] In a preferred embodiment of the present invention, in step two, when laser remelting the second sample, the number of laser melting operations is 1 to 3.

[0036] In a preferred embodiment of the present invention, in step two, during laser remelting, the power of the laser melting emitter is 20W~30W.

[0037] In a preferred embodiment of the present invention, in step three, when the spherical zirconium-niobium-tungsten alloy sample is subjected to cyclic heating and cooling using an electrostatic levitation system, the number of cycles of laser heating and deep undercooling during the electrostatic levitation process is 3 to 6.

[0038] In a preferred embodiment of the present invention, in step three, the transmitter power parameter is 35W~50W when electrostatically levitated.

[0039] This invention utilizes a micro-arc furnace for arc melting to prepare large, homogeneous master alloy button ingots of 800-1000 mg. These ingots are then crushed and packaged to obtain second samples (70-90 mg per group). Due to the small size of the samples, laser heating is used for remelting the smaller materials to obtain spherical pellets with high sphericity, facilitating subsequent electrostatic levitation. Electrostatic levitation is achieved through a containerless process, followed by repeated heating and cooling to achieve deep undercooling, thereby enabling extremely rapid solidification. This effectively controls problems such as solute segregation, and the target alloy can form a single-crystal structure under the provided process parameters.

[0040] The technical solution of the present invention will be further illustrated by specific examples below.

[0041] Example 1 The rapid solidification preparation method for Zr-20Nb-8W zirconium-niobium-tungsten alloy single crystal structures mainly includes the following steps: Step 1: High-purity zirconium, niobium, and tungsten metal surfaces are pre-treated by polishing and cleaning with sandpaper and anhydrous ethanol. The pre-treated raw materials are then packaged into the first sample according to a ratio of 20.0 wt.% Nb, 8.0 wt.% W, and the balance Zr, ensuring a weighing accuracy of 0.1 mg for both batching and subsequent packaging, with a total weight of 800 mg. Button ingots are prepared by two vacuum arc melting processes. Before melting, a high-purity zirconium metal block must be placed in another crucible in the same furnace and melted preferentially to remove impurities. The melting current is 200 A, and the pre-melting vacuum degree is 10. -4 Pa; The button ingots were crushed, reassembled, and repackaged to obtain a second sample, with each sample containing 70 mg.

[0042] Step 2: The second sample is remelted using a laser. The laser melting emitter power is set to 20W, and spherical zirconium-niobium-tungsten alloy samples are obtained by melting once.

[0043] Step 3: The spherical zirconium-niobium-tungsten alloy sample was subjected to three cycles of heating and cooling using an electrostatic levitation system. The emitter power parameter was 35W, and the supercooling degree was 362K, which was then rapidly solidified to form a spherical single crystal zirconium-niobium-tungsten alloy.

[0044] Figure 1 The image shows the EBSD diagram of the zirconium-niobium-tungsten alloy obtained in this embodiment. It can be seen from the image that the Zr-20Nb-8W zirconium-niobium-tungsten alloy has a single crystal structure in the deep supercooled state.

[0045] Example 2 A rapid solidification preparation method for Zr-23Nb-9W zirconium-niobium-tungsten alloy single crystal structures mainly includes the following steps: Step 1: High-purity zirconium, niobium, and tungsten metal surfaces are pre-treated by polishing and cleaning with sandpaper and anhydrous ethanol. The pre-treated raw materials are then packaged into the first sample according to a ratio of 23.0 wt.% Nb, 9.0 wt.% W, and the balance Zr, ensuring a weighing accuracy of 0.1 mg for both batching and subsequent packaging, with a total weight of 900 mg. Button ingots are prepared by three vacuum arc melting processes. Before melting, a high-purity zirconium metal block must be placed in another crucible in the same furnace and melted preferentially to remove impurities. The melting current is 250 A, and the pre-melting vacuum degree is 10. -3 Pa; The button ingots were crushed, reassembled, and repackaged to obtain a second sample, each package containing 90 mg.

[0046] Step 2: The second sample is remelted using a laser. The laser melting emitter power is set to 25W. The sample is melted twice to obtain a spherical zirconium-niobium-tungsten alloy sample. Step 3: The spherical zirconium-niobium-tungsten alloy sample was subjected to four cycles of heating and cooling using an electrostatic levitation system with an emitter power parameter of 42W, resulting in a supercooling degree of 359K, which then rapidly solidified to form a spherical single-crystal zirconium-niobium-tungsten alloy.

[0047] Figure 2 The image shows the EBSD diagram of the zirconium-niobium-tungsten alloy obtained in this embodiment. It can be seen from the image that the Zr-23Nb-9W zirconium-niobium-tungsten alloy has a single crystal structure in the deep supercooled state.

[0048] Example 3 The rapid solidification preparation method for Zr-28Nb-12W zirconium-niobium-tungsten alloy single crystal structures mainly includes the following steps: Step 1: High-purity zirconium, niobium, and tungsten metal surfaces are pre-treated by polishing and cleaning with sandpaper and anhydrous ethanol. The pre-treated raw materials are then packaged into the first sample according to a ratio of 28.0 wt.% Nb, 12.0 wt.% W, and the balance Zr, ensuring a weighing accuracy of 0.1 mg for both batching and subsequent packaging, with a total weight of 1000 mg. Button ingots are prepared by four vacuum arc melting processes. Before melting, a high-purity zirconium metal block must be placed in another crucible in the same furnace and melted preferentially to remove impurities. The melting current is 210 A, and the pre-melting vacuum degree is 10. -4 Pa; The button ingots were crushed, reassembled, and repackaged to obtain a second sample, with each sample containing 80 mg.

[0049] Step 2: The second sample is remelted using a laser. The laser melting emitter power is set to 30W, and the sample is melted three times to obtain a spherical zirconium-niobium-tungsten alloy sample. Step 3: The spherical zirconium-niobium-tungsten alloy sample was subjected to 6 cycles of heating and cooling using an electrostatic levitation system with an emitter power parameter of 50W, resulting in a supercooling degree of 382K, which then rapidly solidified to form a spherical single-crystal zirconium-niobium-tungsten alloy.

[0050] Figure 3 The image shows the EBSD diagram of the zirconium-niobium-tungsten alloy obtained in this embodiment. It can be seen from the image that the Zr-28Nb-12W zirconium-niobium-tungsten alloy has a single crystal structure in the deep supercooled state.

[0051] Comparative Example 1 Step 1: High-purity zirconium, niobium, and tungsten metal surfaces are pre-treated by polishing and cleaning with sandpaper and anhydrous ethanol. The pre-treated raw materials are then packaged into the first sample according to a ratio of 20.0 wt.% Nb, 8.0 wt.% W, and the balance Zr, ensuring a weighing accuracy of 0.1 mg for both batching and subsequent packaging, with a total weight of 800 mg. Button ingots are prepared by two vacuum arc melting processes. Before melting, a high-purity zirconium metal block must be placed in another crucible in the same furnace and melted preferentially to remove impurities. The melting current is 200 A, and the pre-melting vacuum degree is 10. -4Pa; The button ingots were crushed, reassembled, and repackaged to obtain a second sample, with each sample containing 70 mg.

[0052] Step 2: The second sample is remelted using a laser. The laser melting emitter power is set to 20W, and spherical zirconium-niobium-tungsten alloy samples are obtained by melting once.

[0053] Step 3: The spherical zirconium-niobium-tungsten alloy sample was subjected to one cycle of heating and cooling using an electrostatic levitation system with a transmitter power parameter of 35W, resulting in a supercooling degree of 144K.

[0054] Figure 4 The image shows the EBSD diagram of the zirconium-niobium-tungsten alloy obtained in Comparative Example 1. The diagram reveals that the Zr-20Nb-8W zirconium-niobium-tungsten alloy does not have a single-crystal structure. This is because the electrostatic levitation process only completes one laser heating-cooling cycle, preventing the sample from achieving a stable and significant undercooling. This results in a prolonged near-equilibrium solidification time, which is detrimental to the formation of a single-crystal structure.

[0055] Comparative Example 2 Step 1: High-purity zirconium, niobium, and tungsten metal surfaces are pre-treated by polishing and cleaning with sandpaper and anhydrous ethanol. The pre-treated raw materials are then packaged into the first sample according to a ratio of 20.0 wt.% Nb, 18.0 wt.% W, and the balance Zr, ensuring a weighing accuracy of 0.1 mg for both batching and subsequent packaging, with a total weight of 800 mg. Button ingots are prepared by two vacuum arc melting processes. Before melting, a high-purity zirconium metal block must be placed in another crucible in the same furnace and melted preferentially to remove impurities. The melting current is 200 A, and the pre-melting vacuum degree is 10. -4 Pa; The button ingots were crushed, reassembled, and repackaged to obtain a second sample, with each sample containing 70 mg.

[0056] Step 2: The second sample is remelted using a laser. The laser melting emitter power is set to 20W, and spherical zirconium-niobium-tungsten alloy samples are obtained by melting once.

[0057] Step 3: The spherical zirconium-niobium-tungsten alloy sample was subjected to three cycles of heating and cooling using an electrostatic levitation system. The emitter power parameter was 35W, and the supercooling degree was 171K.

[0058] Figure 5 The image shows the EBSD diagram of the zirconium-niobium-tungsten alloy obtained in Comparative Example 2. It can be seen from the image that the Zr-20Nb-18W zirconium-niobium-tungsten alloy has a non-single-crystal structure. This is because although Comparative Example 2 used the same preparation process as Example 1, the W content in Comparative Example 2 was higher, making it difficult to achieve sufficient melting and uniform distribution of W in the sample during preparation, resulting in a polycrystalline structure.

[0059] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, it is intended to include any modifications and variations that fall within the scope of the claims and their equivalents.

Claims

1. A method of producing a single-crystal zirconium niobium tungsten alloy, characterized by, The method comprises the following steps: The surfaces of zirconium, niobium and tungsten metals are polished and cleaned respectively, the raw materials after the pretreatment are divided into first samples according to the target alloy composition, the first samples are vacuum arc melted for multiple times to prepare button ingots, the button ingots are crushed and divided into second samples; The target alloy composition is: Nb 20.0wt.%-28.0wt.%, W 8.0wt.%-12.0wt.%, the balance being Zr and inevitable impurities, and the total amount of each element is 100%; The second samples are remelted by laser to obtain spherical zirconium-niobium-tungsten alloy samples; The spherical zirconium-niobium-tungsten alloy samples are subjected to multiple cyclic heating and cooling by an electrostatic suspension system to form spherical single-crystal zirconium-niobium-tungsten alloy.

2. The production method according to claim 1, characterized by, The electrostatic suspension process adopts laser heating, the power of the electrostatic suspension emitter is 35W-50W, the heating and cooling cycle number is 3-6 times, and the supercooling degree is 350K-385K.

3. The preparation method according to claim 1, characterized in that, Vacuum arc melting, the melting current is 200A~250A, the vacuum degree before melting 10 -4 Pa~10 -3 Pa, vacuum arc melting, a total of 2~4 times of melting.

4. The method of claim 1, wherein, During the vacuum arc melting, a piece of high-purity zirconium metal is additionally put into the same furnace, and the high-purity zirconium metal is firstly melted.

5. The preparation method according to claim 1, characterized in that, During the laser remelting of the second samples, the power of the laser melting emitter is 20W-30W, and the laser melting number is 1-3 times.

6. The method of claim 1, wherein, The specification of the first samples is 800mg / each-1000mg / each, and the specification of the second samples is 70mg / each-90mg / each.

7. The preparation method according to claim 1, characterized in that, The purity of the zirconium, niobium and tungsten metals is not less than 99.9%.

8. A single crystal zirconium niobium tungsten alloy, characterized by, The method is prepared by any one of claims 1-7.

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